> A second strategy out of bounds for privacy preserving products: Interoperability

This part had me scratching my head. Most established non-privacy-preserving products have been slowly killing interoperability because data lock-in provides a moat against users leaving and against potential competitors accessing valuable user data. There's no economic reason why privacy-preserving products should have worse interoperability than privacy-violating ones. Especially in product categories where interoperability does not imply sending PII to third parties.

Edit: Arguably, providing interoperability is easier for products that don't gather a lot of user data because there's less risk of an embarrassing leak of PII if the API is not properly secured.